Coating material recovering device for air knife type coating apparatus

ABSTRACT

The present invention relates to a coating material recovering device which is used in an air knife type coating apparatus. A separating plate is located downstream from the air jet flow blown from a slit-like nozzle after the air jet flow has contacted the surface of a web carrying excess coating material and removed the same. A separating chamber is defined below the separating plate for collecting the excess coating material contained in the air jet flow. Additional separating chambers can be provided for better separation. A means for guiding the air jet flow from which the coating material has been removed is also provided.

nited States Kanda et al.

atet [191 COATING MATERIAL RECOVERING DEVICE FOR AIR KNIFE TYPE COATINGAPPARATUS [75] Inventors: Masao Kanda; Akio Watanabe, both ofFujinomiya, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan [22] Filed: June 20, 1973 [21] Appl. No.: 371,796

[30] Foreign Application Priority Data June 20, 1972 Japan 47-061480 52U.S.C1.Q 118/63, 34/160 [51] Int. Cl. B05c 1I/06 [58] Field of Search.118/63, 102 R, 102 L, 102 A;

[56] References Cited UNlTED STATES PATENTS 2,679,231 5/1954 Pomper etal. 118/63 3,229,447 l/1966 Kosta 118/63 X 3,397,673 8/1968 Mahoney eta1. 118/63 3,550,553 12/1970 Mahoncy et a1. 118/63 3,611,987 10/1971Kohler et al. 118/63 Primary ExaminerMorris Kaplan Attorney, Agent, orFirm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT The presentinvention relates to a coating material recovering device which is usedin an air knife type coating apparatus. A separating plate is locateddownstream from the air jet flow blown from a slit-like nozzle after theair jet flow has contacted the surface of a web carrying excess coatingmaterial and removed the same. A separating chamber is defined below theseparating plate for collecting the excess coating material contained inthe air jet flow. Additional separating chambers can be provided forbetter separation. A means for guiding the air jet flow from which thecoating material has been removed is also provided.

4 Claims, 9 Drawing Figures Pmmggm 1 aims 3, 87 1,325

sum 1 0F 3 PRIOR ART PRIOR ART SHLU 2 UP 3 PRIOR ART WATER COATINGMATERIAL RECOVERING DEVICE FOR AIR KNIFETYPE COATING APPARATUSBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to coating apparatus for applying a coating material to atravelling web such as paper, plastic film and the like, moreparticularly, to a device for recovering the coating material in coatingapparatus of the air-knife type. The air knife type coating apparatus isa continuous coating apparatus employing a slit shape d air jet nozzlefor blowing away excessive coating material applied on the surfaceofthetravelling web by a coating means such as a coating roll, a coatingslit and the like for making a smooth coating surface on the web. Thecoating material recovering device recovers the excessive coatingmaterial blown away by the air jet nozzle and separates the coatingmaterial from the air and discharges the air into the atmosphere.

2. Description of the Prior Art The coating material recovering deviceemployed in air knife type coating apparatus has been called a catchpan," baffle pan or the like, and has heretofore been improved withrespect to various points. However, any type of conventional device forrecovering coating material has disadvantages in practical use, and theefficiency of the recovering device has not been sufficientlyaccomplished. Some conventional coating material recovering devices areshown in FIGS. 1 to 4, in which conventional devices as disclosed in US.Pat. Nos. 3,229,447; 3,397,673; 3,550,553 and Japanese Utility ModelPubln. 33023/1971 are shown.

In the prior art recovering devices as shown in FIGS. 1 to 4, atravelling web h is fed in contact with a coating rollj by means ofaholder roll i and excess coating material picked up from a coating pan lis applied to the web. The coated web m is fed around a backing roll nand an air jet flow (I is blown thereonto from a slit-like nozzle b ofan air doctor a. A separating plate g is provided downstream of the airjet flow (1 (which includes excess coating material c blown away by theair jet) for directing the air jet flow d toward a comparative longguide plate e. Since the air flow including the coating material is noteffectively divided into air and coating material by the top end oftheseparating plate g, rather, the coating material is mixed with the jetair flow while the flow is guided along the guide plate e up to acoating material collecting portion f, and particles of coating materialare scattered by the air jet flow causing clogging of the air doctor androughness in the thickness of the coated layer. Further, upon thescattering of coating material the air around the apparatus iscontaminated and the life of the apparatus is shortened. Thecontaminated air is, of course, harmful to the health of the operatorsof the coating apparatus, and the loss of the coating material due tothe scattering of the coating material reduces the efficiency ofrecovery of the coating material. This is economically a great loss inthe operation of the coating apparatus.

Another defect inherent in such apparatus is that the construction ofthe coating material collecting portion is complicated and it is,accordingly, difficult to clean the inside of the collecting portion ofthe apparatus.

SUMMARY OF THE INVENTION In light of the above defects of conventionalcoating apparatus, the principal object of the present invention is toprovide a device which effectively recovers excess coating materialblown from the surface of a web by an air-jet flowin an air knife typecoating apparatus.

Another object of the present invention is to provide a device whicheffectively separates the coating material from the air flow blown fromthe air jet nozzle and discharges clean air into the atmosphere.

Still another object of the present invention is to provide a devicewhich prevents fine particles ofthe coating material created during theair knife operation of an air knife type coating apparatus from escapinginto the atmosphere.

A further object of the present invention is to provide a coatingmaterial recovering device having a simple interior construction whichcan easily be cleaned by an operator of the coating apparatus.

A still further object of the present invention is to provide a coatingapparatus in which the scattering of the coating material staining theslit nozzle of an air doctor is prevented to obtain a smooth surface anduniform thickness of the coated layer.

Yet a further object of the present invention is to provide a coatingmaterial recovering device particularly adapted to be used in a highspeed air knife type coating apparatus.

The coating material recovering device in accordance with the presentinvention is provided with a first fluid-air separator and a secondfluid-air separator to effectively separate the coating material fromthe air. The first separator comprises a separating plate whichseparates the particles of the liquid coating material from the air jetflow utilizing the difference in inertial moment thereof by use of thetip end of the separating plate. The second separator is a means forutilizing the negative pressure made by the air jet flow or suctionpressure made by a suction fan to form a second air flow blowing intothe coating material recovering portion of the apparatus to direct theair in a different direction. In some embodiments of the presentinvention, the coating material recovering device is provided with athird separator to enhance the effect of separation of fluid and air.

Other objects, features and advantages of the present invention will bemade apparent from the following detailed description of the inventionwith reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 4 are sectional views ofcoating material recovering devices of conventional air-knife coatingapparatus,

FIG. 5 is a schematic side view showing the arrangement of the apparatusin accordance with the present invention,

FIG. 6 is a vertical sectional view of one coating material recoveringdevice in accordance with the present invention,

FIG. 7 is a side elevational view of the same,

FIG. 8 is a vertical sectional view of a coating material recoveringdevice in accordance with another embodiment of the present invention,and

FIG. 9 is a vertical sectional view of the coating material recoveringdevice in accordance with still another embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 5 showingthe overall arrangement of the apparatus of the present invention, acontinuously travelling web 1 is brought into contact with a coatingroll 3 by use of a holder roll 2 and fed around a backing roll 7, whereexcess coating material applied on the surface of the web 6 by means ofa coating pan filled with coating material 4 is blown from the surfaceof the web 6 by means of a high speed airjet flow ejected from aslit-shaped nozzle 9 of an air doctor 8. Thus, a web bearing a coatinglayer of the predetermined thickness is obtained. The coating materialblown away from the surface of the coated web 10 by means of the air jetflow is collected by a coating material recovering device 100 which hasa pair of ducts 101, 102 provided with dampers 103, 104 for controllingthe distribution of air or the flow rate through the coating recoveringdevice 100. The ducts 101 and 102 communicate with a single duct 105which in turn is connected with a fine particle removing device 106which removes extremely fine particles by use of a water shower. Thefine particle removing device 106 is connected with a suction fan 107which pulls the air jet through damper 108, which in turn controls thepulling pressure to provide optimum coating conditions such as coatingspeed, amount of coating material and so forth.

A preferred embodiment of the present invention is shown in FIGS. 6 and7. A travelling web 1 is fed around a holder roll 2 and brought intocontact with a coating roll 3 thereby so that the coating material 4 ina coating material pan 5 is applied to the surface of the web 1 forminga coated web 6. The web 6, bearing excess coating material, is furtherfed around a backing roll 7 where the web 6 is subjected to a high speedair jet flow ejected from the slit-like nozzle 9 of the air doctor 8 sothat the excess coating material is blown off the surface of the web 6to provide a web 10 bearing a predetermined thickness of the coatingmaterial. The coating material removed from the surface of the web 6 bythe high speed air jet flow ejected through the slit nozzle 9 of the airdoctor 8 is discharged into the atmosphere together with the air jetfiow through a coating material recovering device, in which the flow 11mainly composed of coating material is first divided into air andcoating material in the first separating chamber 13. The air flowincluding the coating material in the shape of particles flows along aseparating plate 12 and the coating material of large specific gravityfalls downward from the lower end ofthe separating plate 12 into thefirst separating chamber 13. The air which comes down behind the firstseparating plate 12 moves slowly in the first separating chamber 13,during which time the fine coating material component thereof falls downinto the collected coating material on the bottom of the firstseparating chamber 13. The air jet flow 15 flowing downward along theseparating plate 12 advances further below the separating plate 12.Thus, the first separation ofthe air from the coating material iscompleted.

A part of the excessive coating material mingled in the air jet flow isparticulated into fine particles and guided into the second separatingchamber 17 together with the air jet flow 15. The air jet flow 15containing fine particles and flowing along the separating plate 12 hitsthe wall 16 of the device and moves downward along the interior surfaceof the wall 16 into the second separating chamber 17 provided downstreamthe guide wall 16. The air jet flow containing fine particles 18 islowered in speed when the flow comes into the chamher 17. When itsdirection of advancement changes, particles of a comparatively largespecific gravity 19 are collected on the bottom of the second separatingchamber 17. The coating material 20 collected on the bottom of thesecond separating chamber 17 is discharged through a discharge port 21.

As will be apparent to one skilled in the art, the fields of use of theapparatus present invention are not limited in any manner whatsoever,and it can be used to recover substantially any commonly coated materialwhich is amenable to air knife coating, including separating fineparticles as small as on the order of several microns from particles ofa comparatively high specific gravity, for instance, in the range of 0.3to 3.

Further, the air jet flow 22 containing an extremely small amount offine particles advances along the interior surface of an outer wall 23opposite to wall 16 and hits the bottom wall 24 of the first separatingchamber 13 and changes its direction of advancement and is guided into athird separating chamber 27 defined by internal walls 25 and 26. Whenthe air jet flow 28 flowing into the third separating chamber 27 changesits direction of advancement therein, a part of the coating materialhaving a comparatively large specific gravity 29 is collected on thebottom of the third chamber and is discharged out of discharge port 30.On the other hand, clean air from which the coating material has beenremoved is dishcarged from duct 31 provided on the side wall of thethird separating chamber 27.

Further, if a container 32 forming the third separating chamber 27 isfixed to a frame 33 and the body portion 34 of the coating materialrecovering device 34 is made movable on a rail 37 with wheels 35 and 36provided thereon from the position shown in H6. 6 to the left, externalcovers 38 and 39 and an internal cover 40 can be easily removed togetherwith side cover 41 to make the cleaning of the coating materialrecovering device easy.

FIG. 7 is a side elevation of the coating material recovering device inaccordance with the present invention as shown in FIG. 6, in which atravelling web 1 is brought into contact with a coating roll 3 by meansof a holder roll 2 and a coating material is applied onto the surface ofthe web from a coating material pan 5. The web 6 coated with the coatingmaterial is fed around a backing roll 7, where a high speed air jet flowejected from a slit nozzle 9 of the air doctor 8 is blown against thesurface of the web 6 fed around the backing roll 7 to remove excesscoating material and the air jet flow flows along a separating plate 12and the coating material is discharged from discharging port 14 andrecovered. The separating plate 12 is moved by an air cylinder 43provided on a side plate 42 of the coating material recovering device byway of a crank 44 to control the spacing between the end of theseparting plate 12 and the backing roll 7. The spacing is selected byadjusting a stopper 45 which restricts the movement of the crank 44. Onboth sides of the coating material recovering device on the end plates42 are provided side covers 41 having a duct communicating opening 31,respectively, to discharge air which has been cleaned through the first,second and third separating chambers. The side covers 41 are easilyremovable for cleaning the interior of the coating material recoveringdevice. Further, in order to facilitate the inspection and cleaningofthe interior of the coating material recovering device, exteriorcovers 38 and 39 are made removable and the whole body 34 of the deviceis made horizontally slidable on the rail 37 (leaving the secondseparating chamber 17).

Another embodiment is shown in FIG. 8, wherein a continuously travellingweb 6 carrying excess coating material is fed around a backing roll 7. Ahigh speed air jet flow is ejected from a slit-like nozzle 9 of an airdoctor 8 and blown against the surface of the'web 6 travelling aroundthe backing roll 7 to remove excess coating material 50 therefrom. Thecoating material 50 blown off the web 6 flows along a separating plate52 together with the air jet 51. At the end of the separating plate 52,the coating material 50 having a comparatively large specific gravity isintroduced into the first separating chamber 53 and discharged from thedevice through discharge port 54 and pipe 55 for recovery. On the otherhand, the air jet 51 flows along the separating plate 52 down to thesecond separating chamber 59. During the falling of the airjet flow 51down to the second chamber 59 along partition 56, a portion of the fineparticles of the coating material 57 flowing on the partition 56 withthe air jet are collected by the second separating chamber 59, which isprovided for collecting the liquid particles 57 without obstructing theflow of the air jet 58. The particles collected in the second chamber 59are discharged from the device for recovery. Reference numerals 60 and61, respectively, indicate third and fourth separating chambers definedby partitions 62 and 63 and outer walls 64 and 65 which collect thecoating material 66 and 67 and discharge the collected material out ofthe device through discharging ports 68 and 69, respectively. The aircleaned through the first to fourth separating effect is discharged intothe atmosphere through a duct 70.

Another embodiment of the present invention is shown in FIG. 9, whereina coated web 6 travelling around a backing'roll 7 is subject to an airjet flow ejected from a slit-like nozzle 9 of an air doctor 8 andcoating material 80 is blown from the coated surface of the web 6 andguided along a separation plate 82 together with the air jet 81. At theend ofthe separating plate 82, the coating material 80 is introducedinto a first separating chamber 83 located behind the separating plate82. The collected coating material in the first separating chamber 83 isdischarged from the device through a discharge port 84 and a pipe 85 forrecovery. On the other hand, the air jet flow 81 flows along the surfaceof a partition 86 extending downstream from the separating plate 82 andgoes into a second separating chamber 89 formed by the partition 86 andthe outer portion 87, 88 for separation of fine particles 90 which havenot been collected in the first separating chamber 83. The collectedfine particles 90 are discharged from the discharge port 91 into theair, and the clean air 92 is discharged through a duct 93.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:

l. in a coating apparatus, means for removing and recovering excesscoating material from a web coated in an air knife coating apparatus,said removing and re- 6 covering apparatus comprising:

a. means for applying a flowing gas stream tangentially to the web forremoving excess coating material from the web which is entrained in theflowing gas stream;

b. a separating plate adjacent said web extending transversely to theflow path of the flowing'gas stream containing the excess coatingmaterial downstream of the contact area of the flowing gas stream withthe web for separating excess coating material from the flowing gasstream;

c. a drip pan underlying said separating plate to catch liquid materialflowing downwardly on the separating plate undergravity influence;

d. means including said drip pan forming a first chamber for recovery ofsaid excess coating material, the improvement wherein:

e. said first chamber includes chamber wall means to the side of saidseparating plate opposite the means applying the flowing gas stream,spaced from said plate and extending from said drip pan to the vicinityof said web to form with said drip pan and said separating plate avolume in which separated air moves slowly downwardly behind theseparating plate to cause the fine coating material component thereof togravity deposit into said underlying drip pan; and wherein f. saidseparating plate is positioned with respect to said gas stream, said weband said drip pan such that the flowing gas stream does not directlyenter said first chamber and re entrain substantial amounts of alreadyseparated coating material during gravity deposit from said separatingplate into said drip pan.

2. Apparatus as defined in claim 1 further comprising wall meansdisposed generally in line with said separating plate, and extendingdownwardly from said drip pan in the direction of flow of said gasstream after deflection by said separating plate to guide the airdownstream of said first chamber, and said apparatus further comprisingadditional liquid collecting means, said means comprising a troughlocated on said guide wall at a location which does not obstruct theflow of air along said guide wall.

3. Apparatus as defined in claim 1 further comprising means fordischarging the air jet flow from said apparatus after the coatingmaterial has been removed, said discharging means being provided on atleast one side of said apparatus for discharging said air flow into theatmosphere.

4. Apparatus as defined in claim 1 further comprising a secondseparating chamber provided downstream and below said first separatingchamber including coating material collecting means at the bottomportion thereof, said second chamber being separable from said firstseparating chamber, and wherein said first separating chamber includeswheels operatively coupled thereto for moving said first chamberlaterally relative to said underlying separating chamber and saidapparatus further comprising means for fixing said second separatingchamber to a stationary base member upon

1. In a coating apparatus, means for removing and recovering excesscoating material from a web coated in an air knife coating apparatus,said removing and recovering apparatus comprising: a. means for applyinga flowing gas stream tangentially to the web for removing excess coatingmaterial from the web which is entrained in the flowing gas stream; b. aseparating plate adjacent said web extending transversely to the flowpath of the flowing gas stream containing the excess coating materialdownstream of the contact area of the flowing gas stream with the webfor separating excess coating material from the flowing gas stream; c. adrip pan underlying said separating plate to catch liquid materialflowing downwardly on the separating plate under gravity influence; d.means including said drip pan forming a first chamber for recovery ofsaid excess coating material, the improvement wherein: e. said firstchamber includes chamber wall means to the side of said separating plateopposite the means applying the flowing gas stream, spaced from saidplate and extending from said drip pan to the vicinity of said web toform with said drip pan and said separating plate a volume in whichseparated air moves slowly downwardly behind the separating plate tocause the fine coating material component thereof to gravity depositinto said underlying drip pan; and wherein f. said separating plate ispositioned with respect to said gas stream, said web and said drip pansuch that the flowing gas stream does not directly enter said firstchamber and reeNtrain substantial amounts of already separated coatingmaterial during gravity deposit from said separating plate into saiddrip pan.
 2. Apparatus as defined in claim 1 further comprising wallmeans disposed generally in line with said separating plate, andextending downwardly from said drip pan in the direction of flow of saidgas stream after deflection by said separating plate to guide the airdownstream of said first chamber, and said apparatus further comprisingadditional liquid collecting means, said means comprising a troughlocated on said guide wall at a location which does not obstruct theflow of air along said guide wall.
 3. Apparatus as defined in claim 1further comprising means for discharging the air jet flow from saidapparatus after the coating material has been removed, said dischargingmeans being provided on at least one side of said apparatus fordischarging said air flow into the atmosphere.
 4. Apparatus as definedin claim 1 further comprising a second separating chamber provideddownstream and below said first separating chamber including coatingmaterial collecting means at the bottom portion thereof, said secondchamber being separable from said first separating chamber, and whereinsaid first separating chamber includes wheels operatively coupledthereto for moving said first chamber laterally relative to saidunderlying separating chamber and said apparatus further comprisingmeans for fixing said second separating chamber to a stationary basemember upon which said wheels ride.